A couple weeks a go I posted ArcGIS Pro Create Locator fails : Turns out the create locator tool is very sensitive to empty geometries but the error returned upon failure is rather ambiguous: "Error happened while transforming data".
In an email today from ESRI I'm told bug-000123955 has been resolved and the fix will appear in release 2.5.
Thanks Eric Anderson and Shana Britt.
That should just about do it....